1. Field of the Invention
The present invention relates to a controller for a cooling system comprising a low-temperature showcase set in a supermarket or the like, and a refrigerating machine for supplying refrigerant to the low-temperature showcase, for example.
2. Description of the Related Art
It has been general that a plural of low-temperature showcases such as freezing/refrigerating showcases or the like are installed in a store such as a supermarkets or the like and they are supplied to display and sold foods while freezing/refrigerating these foods. From the viewpoint of attempts to environmental problems and reduction of energy cost, it has been also recently recognized as an important matter in stores such as supermarkets, etc. to take countermeasures to reduce power consumption of a cooling system having low-temperature showcases. In order to reduce the power consumption, it is important to enhance the operation efficiency of the low-temperature showcases and the refrigerating machine themselves, however, it is also possible to reduce power consumption in consideration of the cooperation of the respective parts constituting the cooling system containing the low-temperature showcases and the refrigerating machine.
Therefore, there has been proposed a technique of targeting an invert type refrigerating machine, setting a low-pressure side pressure value of the refrigerating machine and setting an inverter frequency on the basis of the low-pressure side pressure value to reduce the power consumption (for example, JP-A-Hei-9-217974).
In general, when the low-pressure side pressure of the refrigerating machine is set to a low value, the cooling power of the refrigerating machine is high, and thus the cooling temperature of the low-temperature showcase decreases, so that the cooling state (cooling condition) is kept excellent. Conversely, when the low-pressure side pressure is set to a high value, the cooling power of the refrigerating machine is lowered, however, the power consumption is reduced. That is, in the control of the refrigerating machine based on the setting of the low-pressure side pressure, the energy saving operation and the excellent cooling state have conflicting relation to each other, and it has been hitherto general that the excellent cooling state has priority over the energy saving operation and thus the low-pressure side pressure is set to a low value.
The required cooling power of the refrigerating machine is changed in accordance with the operation environmental condition such as the load state of the low-temperature showcase or the like. Therefore, there has been recently proposed a technique of automatically the low-pressure side pressure value in accordance with the operation environmental condition, thereby satisfying both the securement of the excellent cooling state and the energy saving operation. This technique has a data base for storing a set value of optimum low-pressure side pressure (hereinafter referred to as “low-pressure side pressure set value”) every operation environmental condition. According to this technique, the operation is executed for a while under some operation environmental condition, and the optimum low-pressure side pressure set value is learned under the operation environmental condition concerned. when the operation environmental condition concerned comes afterwards, the low-pressure side pressure is quickly set to the set value of the optimum low-pressure side pressure (see JP-A-2004-57347, for example).
The operation environmental condition contains parameters such as a time zone, air temperature, etc. For example, even in the same time zone, the temperature is greatly varied in accordance with the difference in season, day or the like. Therefore, there is a case where it takes several days or more to learn the set value of the optimum low-pressure side pressure for some operation environmental condition.
Furthermore, at the start time of the operation, the set value of the optimum low-pressure side pressure under the operation environmental condition at that time has not yet been registered and thus it is under unlearned state. In the case of the operation under an unlearned operation environmental condition, the operation is executed with a low-pressure side pressure set value with which no energy saving effect is obtained until the learning is completed. However, as descried above, it takes relative long time to complete the learning for some operation environmental condition, and thus the period for which the energy saving is not obtained is increased.